feat(pi): add update PR mode

[BillLeoutsakosvl346]

Stacked PR

This PR is stacked on #5962 and intentionally targets feature/pi-babysit. PR #5962 remains unchanged and targets staging.

Do not merge this PR before #5962. After #5962 merges, this branch will be rebased onto the merged Babysit tree on staging, retargeted to staging, and revalidated.

Summary

Add Update PR (cloud_branch) as the fourth Pi mode, with Create PR permission and Babysit parity.

• Check out one exact existing remote branch and push HEAD back with a normal non-force refspec.
• Find the exact open same-repository PR for that branch; update it when found and create it when missing.
• Reuse Base Branch, PR Title, PR Body, and a tri-state PR State control (preserve, draft, ready). Blank metadata preserves an existing PR and is generated for a new PR.
• Reuse Create PR memory, skills, search, BYOK, streaming, authoring, Babysit, budgets, outputs, and GitHub permission model.
• Complete the initial non-force push before any PR mutation. A rejected push prevents PR changes and Babysit; a no-change run still creates or updates the PR.
• With Babysit, ensure the PR is ready, create it if missing, and feed its number into the existing continuation.
• Fail closed on ambiguous, forked, closed, moved, or mismatched PRs. Never merge, rebase, retry, or force-push at runtime.

Security Boundaries

• The GitHub token is used only by host GitHub operations and sandbox clone/push commands; it is absent from Pi and commit/diff preparation.
• Model and optional search keys are scoped to Pi and absent from clone, commit/diff preparation, push, and host PR operations.
• PR coordinates are validated before and after authoring, and surfaced text/errors are scrubbed against all sandbox credentials.
• Existing Babysit pinning, reviewer trust, budgets, and lifetime limits are reused unchanged.

Permissions

Create PR and Update PR require the same GitHub permissions:

• Fine-grained token: Contents: Read and write and Pull requests: Read and write.
• Classic token: repo scope, with organization SSO authorization when required.
• Babysit additionally needs the existing issue-comment, review-thread, Actions, commit-status, and check reads/writes documented for Create PR.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation
• Other

Testing

• All Pi suites: 20 files / 293 tests passed before the final two focused regression additions; the final focused suites pass 67 tests.
• Sim TypeScript type-check passed.
• Biome passed for all touched TypeScript files.
• Fumadocs MDX generation passed.
• Monorepo boundary and API validation audits passed.

Review focus: exact PR discovery/revalidation, push-before-PR sequencing, missing-PR creation, metadata/draft transitions, no-op finalization, non-fast-forward failure, Babysit reuse, and credential isolation.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement

Screenshots/Videos

Not included: this is a cloud-gated block option and behavior is covered by block visibility and handler/backend tests.

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Project	Deployment	Actions	Updated (UTC)
docs	Ready	Preview	Jul 30, 2026 1:11am

[BillLeoutsakosvl346]

@greptileai

[BillLeoutsakosvl346]

cursor review

[cursor]

PR Summary

Medium Risk
New GitHub write paths (branch push, PR create/update, draft transitions) and sandbox credential handling; mitigated by push-before-PR ordering, strict PR matching, secret scrubbing, and broad tests.

Overview
Adds a fourth Pi Coding Agent mode, Update PR (cloud_branch), for continuing work on an existing remote branch instead of always creating a new one.

The sandbox checks out that branch, runs Pi, non-force pushes HEAD back, then finds or creates the matching open same-repo PR. Host logic updates title/body/base when set, applies PR State (preserve / draft / ready) via GraphQL where needed, and re-validates PR identity after authoring (ambiguous, fork, or moved-head cases fail closed). A failed push blocks PR changes and Babysit; a no-op edit can still create or update the PR.

Create PR and Update PR now share sandbox authoring, BYOK for the model key, skills/memory/search, Babysit controls/outputs, and the same GitHub token permission model. Babysit copy is generalized from “after Create PR” to “after authoring.” Standalone babysit mode is rejected with a migration message.

^{Reviewed by Cursor Bugbot for commit 4d22771. Bugbot is set up for automated code reviews on this repo. Configure here.}

[greptile-apps]

Greptile Summary

Adds Update PR (cloud_branch) as a fourth Pi mode with Create PR parity for sandbox authoring, non-force push, PR create/update, and Babysit.

• New cloud_branch mode in the Pi block UI with Target Branch, PR State, shared Base/Title/Body, skills, memory, search, and Babysit controls.
• Cloud backend checks out an existing branch, pushes without force, then finds or creates the exact open same-repo PR and applies metadata/draft transitions.
• GitHub helpers add open-PR-by-branch lookup and GraphQL draft/ready transitions; docs and tests cover discovery, no-op finalization, push failures, and Babysit reuse.

Confidence Score: 5/5

The PR appears safe to merge from this follow-up pass; no prior Greptile findings remain outstanding and no eligible new inline issues were identified.

No blocking failure remains.

Important Files Changed

Filename	Overview
apps/sim/executor/handlers/pi/cloud-backend.ts	Shared authoring path for Create/Update PR with push-before-PR sequencing, ensure/update PR finalization, and Babysit handoff.
apps/sim/executor/handlers/pi/github-pr.ts	Open-PR-by-branch discovery with same-repo revalidation and GraphQL draft/ready state changes.
apps/sim/blocks/blocks/pi.ts	Exposes Update PR mode and field conditions for target branch, PR state, and shared authoring/Babysit controls.
apps/sim/executor/handlers/pi/pi-handler.ts	Parses cloud_branch inputs (targetBranch, prState) and routes BYOK/authoring like Create PR.

Sequence Diagram

sequenceDiagram
  participant Block as Pi block (cloud_branch)
  participant Host as cloud-backend
  participant SB as Sandbox
  participant GH as GitHub

  Block->>Host: run Update PR
  Host->>GH: findOpenPrForBranch (preflight)
  Host->>SB: clone target branch
  Host->>SB: Pi authoring (no GitHub token)
  Host->>SB: prepare commit/diff
  alt has changes
    Host->>SB: non-force push HEAD
    SB->>GH: push refs/heads/target
  end
  Host->>GH: findOpenPrForBranch (post-push)
  alt open PR found
    Host->>GH: update metadata / draft state
  else none
    Host->>GH: create PR
  end
  opt Babysit enabled
    Host->>GH: ready PR + continuation
  end

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[BillLeoutsakosvl346]

Demo:

Screen.Recording.2026-07-28.at.5.26.08.PM.mov

[BillLeoutsakosvl346]

@greptileai

[BillLeoutsakosvl346]

@greptileai

[BillLeoutsakosvl346]

@greptileai

[BillLeoutsakosvl346]

@greptileai

[BillLeoutsakosvl346]

@greptileai

[BillLeoutsakosvl346]

@greptileai

[BillLeoutsakosvl346]

@greptileai

[BillLeoutsakosvl346]

cursor review

[BillLeoutsakosvl346]

@greptileai

[BillLeoutsakosvl346]

cursor review

[BillLeoutsakosvl346]

@greptileai

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 5aaf5fd. Configure here.}

[BillLeoutsakosvl346]

cursor review

[BillLeoutsakosvl346]

@greptileai

[cursor]

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 4d22771. Configure here.}